The present invention generally relates to liquid heating apparatus and, in representatively illustrated embodiments thereof, more particularly provides a specially designed, pumpless combination instantaneous/storage water heater system.
The on-demand supply of hot water to plumbing fixtures such as sinks, dishwashers, bathtubs and the like has for years been achieved using fuel-fired or electric water heaters in which a relatively large water storage tank is provided with a fuel-fired burner or one or more electric heating elements controlled to maintain pressurized, tank-stored water at a selectively variable delivery temperature—typically around 120 degrees Fahrenheit. Pressurized cold water from a source thereof is piped to the tank to replenish hot water drawn therefrom for supply to one or more plumbing fixtures operatively connected to the water heater.
Another conventional way of providing an on-demand supply of hot water to various plumbing fixtures is to use a tankless of “instantaneous” water heater in which water is flowed through a high heat input heat exchanger, without appreciable water storage capacity, so as to provide only as much hot water as needed by the open fixture(s). Where higher hot water flow rates than the instantaneous water heater can provide at the desired heated temperature are required, it has been conventional practice to connect a storage tank to the instantaneous water heater, in series therewith, to augment the hot water delivery capability of the instantaneous water heater with pre-heated storage tank water.
According to another conventional practice, a hot water recirculating loop with a circulating pump therein is operatively coupled to one or both of the instantaneous heater and storage tank to provide even faster delivery of hot water to the served fixtures. Despite the overall hot water production and delivery improvements provided by these conventional instantaneous/tank type water heater combinations, they present several well known problems, limitations and disadvantages.
For example, the necessity of providing a pump and its necessary controls undesirably builds in additional cost and complexity to the overall hot water supply system. Additionally, conventional combination systems of this general type tend to have rather rudimentary control formats with respect to efficiently coordinating the operation of the instantaneous water heater and associated storage tank from both flow rate and temperature control perspectives.
It would thus be desirable to provide an improved combination instantaneous/tank type water heater system in which (1) the circulating pump, with its attendant complexity and cost, was eliminated, and (2) the system was provided with improved temperature and flow rate control. It is to this design goal that the present invention is primarily directed.